Diabetes
Diabetes mellitus is a major global health problem which is inadequately treated by available drugs. The International Diabetes Federation has estimated that over 100 million people worldwide are afflicted with this disease. Diabetes costs the American economy over $100 billion annually, according to a study reported in the Journal of Clinical Endocrinology and Metabolism, which went on to say that ". . . health care expenditures for people with diabetes constituted about one in seven health care dollars spent in 1992. " Moreover, the American Medical Association reports that the incidence of diagnosed diabetes as a percentage of the American population has tripled since 1958, and that the total number of diagnosed and undiagnosed cases has grown to about 16 million.
Diabetes is the name given to the clinical description of patients with a number of symptoms arising from raised blood glucose levels. The metabolism of glucose involves many organs, in each of which several important metabolic steps occur. Key regulatory points include hepatic regulation of glucose uptake and release, muscle utilization of fuels, control by pancreatic production of insulin and glucagon, and neurogenic controls. Diabetes may arise from abnormalities at one or several sites in the complex feedback loops in this system.
Two main types of diabetes can be distinguished: (1) insulin-dependent diabetes mellitus (previously termed "juvenile-onset," and now called "IDDM" or "Type 1"), and (2) non-insulin-dependent diabetes mellitus (previously ermed "maturity-onset," and now called "NIDDM" or "Type 2"). Other forms of diabetes include (3) maturity-onset or non-insulin-dependent diabetes in the young (a rare dominantly inherited, mild type of disease); (4) diabetes mellitus or carbohydrate intolerance associated with certain genetic syndromes; (5) secondary diabetes mellitus (e.g., drug-induced, from pancreatic disease, hormonal or receptor abnormalities, etc.), and (6) gestational diabetes mellitus. Different nomenclatures for these types have arisen because overlap between the types has made a strict, simple classification covering all patients difficult.
Typically, diabetes occurs when the pancreas no longer produces enough insulin, a hormone that regulates the metabolism of blood glucose. In Type 1 diabetes, which afflicts about 10% of all people with diagnosed diabetes in developed countries, the pancreatic beta cells that make insulin have been destroyed. In the more prevalent form of diabetes, Type 2 diabetes, the insulin-producing cells are unable to produce enough insulin to compensate for the patient's poor sensitivity to the hormone in glucose-using tissues such as skeletal muscle (a condition called insulin resistance). In both Type 1 and Type 2 diabetes, the insulin deficiency results in an abnormally high blood-glucose concentration (a condition called hyperglycemia) hich is an important cause of the degenerative complications associated with diabetes, including blindness, kidney failure and nerve damage. In addition, many authorities believe hyperglycemia plays a role in the development of heart disease.
One of the main features of Type 1 diabetes is the sudden appearance in non-obese children or young adults of a severe disease which only responds satisfactorily to insulin therapy. On the other hand, Type 2 patients tend to present at an older age, are often obese and then respond to diet, without need for insulin therapy. The "juvenile" diabetes and "maturity" diabetes nomenclature based on the age of onset has fallen out of fashion with the realization that auto-immunity to the islets is the characteristic pathology of Type 1 diabetes, and that this is not confined to juvenile-onset but can occur in maturity-onset diabetes and may present at any age. However, the distinction based on age is still sometimes used as a shorthand description of presentation.
The advent of insulin therapy led to the clinical classification of the two main types of diabetes as "insulin-dependent" and "non-insulin-dependent," which relate to the empirical requirement for insulin therapy. This was introduced because some maturity-onset diabetic patients are of normal weight, have severe disease which requires insulin, and resemble juvenile-onset diabetic patients. Although IDDM is defined by the patient's dependence on insulin for survival, in practice this definition is often extended to include patients who require insulin therapy to prevent symptoms. Similarly, the term NIDDM is often restricted to patients who can be maintained symptom-free either by diet or by tablet therapy. This usage is not strictly correct because, as noted below, patients who present with NIDDM may later develop more severe diabetes that requires insulin therapy. In practice, a Type 2 patient initially treated by diet or tablets, but later transferred to insulin, is often termed an insulin-treated NIDDM patient.
Insulin
Since its discovery in 1921, insulin replacement therapy has played a central role in treating diabetes. For people with Type 1 diabetes, insulin injections are essential, since these patients would otherwise die. For people with Type 2 diabetes, oral medications that either stimulate greater insulin production or enhance insulin sensitivity may improve metabolic control. However, as many as 20% of people with newly diagnosed Type 2 diabetes do not respond to oral therapy. Moreover, patients who do respond to oral therapy become progressively resistant over time, with as many as 10% each year ceasing to derive a therapeutic benefit. Thus, an estimated 40% of people diagnosed with Type 2 diabetes are using insulin injections to manage their disease. It has been estimated that in North America, Europe and Japan alone, as many as two million people with Type 1 diabetes and five million people with Type 2 diabetes use insulin to help control their blood-glucose concentrations.
Because insulin given by mouth is digested as a dietary protein, it has to be administered by injection. Various advances and changes have been made in the United States and Europe in the purity and formulation of insulin preparations. These have resulted in the marketing of mono-species insulins (porcine, bovine, and human) of very high purity. Human insulin is most commonly synthesized in either E. coli or yeast cells that have been genetically altered by recombinant DNA technology, but may also be prepared by a semi-synthetic process from porcine insulin.
Prior to 1973, insulin preparations available for therapeutic use contained, as potentially antigenic components, significant amounts of proinsulin and its incompletely converted products as well as other pancreatic hormones. New procedures were devised to prepare purer preparations of the hormone. Two such preparations are "single-peak" insulin and "single-component" insulin; the latter is designated as "purified." The purity of commercial insulin in the United States is now at least that of "single-component" insulin (99%). These "purified" insulins contain not more than 10 parts per million of proinsulin. "Purified" porcine insulin is the least immunogenic of the nonhuman insulins available.
All regular insulin preparations in the United States are now supplied at neutral pH. This has resulted in improved stability of the hormone, and patients need no longer refrigerate the vial of insulin in use. Furthermore, neutral regular insulin can be mixed in any desired proportion with other, modified insulin preparations since all marketed insulin preparations will be at a similar pH. Preparations of insulin have been divided into three general categories according to promptness, duration, and intensity of action following subcutaneous administration. They are classified as fast-, intermediate-, and long-acting insulins. There are also various types of insulins within these categories. They include regular insulins, protamine zinc insulins, NPH insulins, semilente insulins (prompt insulin zinc suspensions), lente insulins (insulin zinc suspensions), and ultralente insulins (extended insulin zinc suspensions).
Crystalline insulin is prepared by the precipitation of the hormone in the presence of zinc (as zinc chloride) in a suitable buffer medium. Crystalline insulin when dissolved in water is also known as regular insulin. Following subcutaneous injection, it is rapidly absorbed (15-60 minutes). Its action is prompt in onset and relatively short in duration, i.e., it reaches its peak effect in about 1.5 to 4 hours, and lasts for about 5-9 hours.
By permitting insulin and zinc to react with the basic protein protamine, Hagedorn and associates prepared a protein complex, protamine zinc insulin. When this complex is injected subcutaneously in an aqueous suspension, it dissolves only slowly at the site of deposition, and the insulin is absorbed at a retarded but steady rate. Protamine zinc suspension insulin has largely been replaced by isophane insulin suspension, also known as NPH insulin; the N denotes a neutral solution (pH 7.2), the P refers to the protamine zinc insulin content, and the H signifies the origin in Hagedorn's laboratory. It is a modified protamine zinc insulin suspension that is crystalline. The concentrations of insulin, protamine, and zinc are so arranged that the preparation has an onset and a duration of action intermediate between those of regular insulin and protamine zinc insulin suspension. Its effects on blood sugar are indistinguishable from those of an extemporaneous mixture of 2 to 3 units of regular insulin and 1 unit of protamine zinc insulin suspension.
Chemical studies have revealed that the solubility of insulin is determined in important measure by its physical state (amorphous, crystalline, size of the crystals) and by the zinc content and the nature of the buffer in which it is suspended. Insulin can thus be prepared in a slowly absorbed, slow-acting form without the use of other proteins, such as protamine, to bind it. Large crystals of insulin with high zinc content, when collected and resuspended in a solution of sodium acetate-sodium chloride (pH 7.2 to 7.5), are slowly absorbed after subcutaneous injection and exert an action of long duration. This crystal preparation is named extended insulin zinc suspension (ultralente insulin). Amorphous insulin precipitated at high pH is almost as rapid in onset than regular insulin, but has a somewhat longer duration of action. This amorphous preparation is named prompt insulin zinc suspension (semilente insulin). These two forms of insulin may be mixed to yield a stable mixture of crystalline (7 parts) and amorphous (3 parts) insulin--called insulin zinc suspension (lente insulin)--that is intermediate in onset and duration of action between semilente and ultralente preparations and is similar to NPH insulin.
In summary, the fast-acting insulins include the regular insulins and the prompt insulin zinc suspensions (semilente insulins). The intermediate-acting insulins include the isophane insulin suspensions (NPH insulins, isophane insulin) and the insulin zinc suspensions (lente insulins). The long-acting insulins include protamine zinc insulin suspensions, and extended insulin zinc suspensions (ultralente insulins). Most of these preparations are available as either porcine or bovine insulins. Human insulins of recombinant DNA origin are available as regular and isophane insulins and as insulin zinc suspensions. Recently, a modified insulin (Lys(B28), Pro(B29) human insulin analog, created by reversing the amino acids at positions 28 and 29 on the insulin B-chain) has been introduced. It is a fast-acting insulin, with a more rapid onset of glucose lowering action, an earlier peak action, and a shorter duration of action than regular human insulin.
Many insulins are available from a number of companies. These include Eli Lilly & Company and Novo Nordisk, two of the largest suppliers of insulin in the world. Fast-acting insulins available from Eli Lilly include (1) Iletin.RTM. I (Regular); (2) Regular Iletin.RTM. II (Pork, 100 Units); (3) Regular Iletin.RTM. II (Concentrated, Pork, 500 Units); (4) Humalog.RTM. Injection (insulin lyspro, recombinant DNA origin); and (5) Humulin.RTM. R (regular insulin, recombinant DNA origin, 100 Units). Fast-acting insulins available from Novo Nordisk include (1) Novolin.RTM. R (Regular, Human Insulin Injection (recombinant DNA origin) 100 Units); (2) Novolin.RTM. R PenFill 1.5 ml Cartridges (Regular, Human Insulin Injection (recombinant DNA origin) 100 Units); (3) Novolin.RTM. R Prefilled.TM. (Regular, Human Insulin Injection (recombinant DNA origin) in a 1.5 ml Prefilled Syringe, 100 units/ml); (4) Regular Purified Pork Insulin (100 Units/ml); and (5) Velosulin.RTM. BR (Buffered Regular Human Insulin Injection, 100 Units/ml). Intermediate-acting insulins available from Eli Lilly include (1) Humulin.RTM. 50/50 (50% human insulin isophane suspension and 50% human insulin injection (rDNA origin), 100 Units); (2) Humuline.RTM. 70/30 (70% human insulin isophane suspension and 30% human insulin injection (rDNA origin), 100 Units); (3) Humulin.RTM. L (lente; human insulin (rDNA origin) zinc suspension, 100 Units); ); (4) Humulin.RTM. N (NPH; human insulin (rDNA origin) isophane suspension, 100 Units); (5) Lente.RTM. Iletin.RTM. I, (insulin zinc suspension, beef-pork); (6) NPH Iletin.RTM. I (isophane insulin suspension, beef-pork); (7) Lente Iletin.RTM. II (insulin zinc suspension, purified pork); and (8) NPH Iletin.RTM. II, (isophane insulin suspension, purified pork). Intermediate-acting insulins available from Novo Nordisk include (1) Novolin.RTM. L (Lente, Human Insulin Zinc Suspension (recombinant DNA origin), 100 Units/ml); (2) Novolin.RTM. N (NPH, Human Insulin Isophane Suspension (recombinant DNA origin), 100 Units/ml); (3) Novolin.RTM. N PenFill.RTM. 1.5 ml Cartridges; (4) Novolin.RTM. N Prefilled.TM. (NPH, Human Insulin Isophane Suspension (recombinant DNA origin) in a 1.5 ml Prefilled Syringe, 100 Units/ml); (5) Novolin.RTM. 70/30 (70% NPH, Human Insulin Isophane Suspension and 30% Regular, Human Insulin Injection (recombinant DNA origin), 100 Units/ml); (6) Novolin.RTM. 70/30 PenFill.RTM. 1.5 ml Cartridges; (7) Novolin.RTM. 70/30 Prefilled.TM. (70% NPH, Human Insulin Isophane Suspension and 30% Regular, Human Insulin Injection (recombinant DNA origin) in a 1.5 ml Prefilled Syringe, 100 Units/ml); (8) Lente Purified Pork Insulin (Zinc Suspension, USP 100 Units/ml); and (9) NPH Purified Pork Isophane Insulin Suspension (100 Units/ml). Long acting insulins include Eli Lilly's Humulin.RTM. U (Ultralente.RTM. human insulin (recombinant DNA origin) extended zinc suspension).
Normal people produce half their insulin at a low, basal rate and half in response to meals. The insulin response to meals occurs within 5 minutes and lasts for 2-3 hours following each meal. Despite 75 years of efforts to improve insulin therapy, most people with diabetes have great difficulty achieving optimal glucose control with insulin alone. For superior glucose control, each insulin injection should be adjusted to reflect the person's pre-meal blood-glucose concentration, the carbohydrate content of the meal, and the individual's planned level of physical activity. The basal insulin supply can be given to diabetic patients using a long-acting, crystalline insulin which is slowly absorbed. The major difficulty comes in coping with meals, since soluble insulin takes 30 minutes to be absorbed from a subcutaneous injection (i.e., it should be given 30 minutes before a meal) and lasts for 4-6 hours. This long time-course is inconvenient and a snack often has to be taken 2-3 hours after injection to cover the prolonged insulin absorption. In addition, absorption of insulin varies from injection to injection. The insulin requirements of a patient are also less after exercise and greater when stressed or ill. Therefore, most patients continue to have high glucose levels, and aggressive efforts to bring blood-glucose concentration down into the normal range (a condition called normoglycemia) using intensive insulin therapy increase the risk of blood-glucose concentration falling too low (a condition called hypoglycemia), which can cause unpleasant and dangerous effects including sweating, disorientation, personality changes, coma, convulsions and even death. If normoglycemia is to be achieved, patients need to be attentive to their life-style and assess the response to their insulin therapy by measuring their blood glucose. This is done by pricking a finger and placing the blood onto a strip containing the enzyme glucose oxidase; the glucose concentration is determined either by an electronic sensor or by a color change monitored visually. Many patients do this regularly four times per day, before meals and before bed, in order to assess the appropriate insulin doses, although others find this unacceptable. Indeed, to avoid hypoglycemia, many people with diabetes maintain high blood-glucose concentrations and thereby increase their risk of degenerative complications from the disease.
Diet therapy, inducing weight reduction, may be sufficient to reduce the blood glucose to below the renal threshold and to make people with Type 2 diabetes symptom-free, although it is rarely sufficient to induce normal fasting glucose levels. If symptoms persist despite dietary therapies, then most physicians treat with tablets containing sulphonylureas to stimulate insulin secretion. This approximately doubles the .beta.-cell efficiency, but, nevertheless, continued symptom-free hyperglycemia with a fasting glucose level of 9-10 mmol/l is common. "Second generation" drugs such as glibenclamide or glipizide are no more effective than "first generation" drugs such as tolbutamide or chlorpropamide. Biguanide therapy with metformin, to improve glucose uptake is an alternative, but like a sulphonylurea it only induces a modest decrease of blood glucose. If symptoms recur on diet and tablet therapy, patients are transferred to insulin therapy.
Although most people with diabetes cannot maintain their blood glucose concentrations near the normal range with insulin alone, it is now established that even modest improvements in glucose control can result in significant reductions in the risk of degenerative complications such as blindness, kidney failure and nerve damage. In other words, the maintenance of a normal blood glucose concentration has been shown to prevent diabetic complications and maintain health.
In June 1993, the National Institutes of Health announced the results of the Diabetes Control and Complications Trial ("DCCT"). This decade-long, prospective study of over 1,400 people with Type 1 diabetes established the importance of glucose control as a determinant of long-term risk of degenerative complications. The quality of glucose control for each DCCT participant was determined by measuring the proportion of blood-hemoglobin which had chemically combined with blood-glucose to form glycated hemoglobin (HbA1c). This measurement is a recognized indicator of average blood-glucose concentration over the three- to four-month period prior to testing, and lower glycated hemoglobin values are indicative of better glucose control. In this regard, the data from the DCCT showed definitively that the risk of degenerative complications is greatly reduced if blood-glucose concentrations in people with Type 1 diabetes can be brought closer to the concentrations measured in non-diabetic individuals. However, the intensive insulin therapy used to achieve this benefit had several side effects and disadvantages, including (1) a three-fold increase in severe hypoglycemia (defined as low blood sugar episodes which rendered the individual incapable of treating themselves such that the intervention of another person was required compared) with the control group, (2) an average weight gain of 10 to 15 pounds per patient, (3) a highly burdensome treatment regimen requiring strict patient compliance, and (4) intensive and costly support from diabetes care-givers. As a result of these side effects and disadvantages, most people using insulin currently are unable to achieve normal blood-glucose concentrations.
Thus, advances in insulin preparations have not led to the elimination of hyperglycemia, which in turn leads to the degenerative complications of diabetes. It is understood that, in order to achieve normoglycemia in most patients, new technology will need to be developed. In view of the health problems and economic costs associated with this failure to achieve optimal glucose control a new drug which could safely help people with diabetes improve their glucose control without imposing unacceptable treatment burdens would be of great therapeutic benefit.
Amylin
In 1987, researchers at the University of Oxford reported that the pancreatic beta-cells which make insulin also produce a second peptide, amylin. Amylin is a 37 amino acid protein hormone that is co-secreted with insulin from the beta cells of the pancreas in response to a meal. This hormone in healthy individuals is believed to work in concert with insulin in controlling glucose metabolism. The structure and biology of amylin have previously been reviewed. See, for example, Rink et al., Trends in Pharmaceutical Sciences, 14:113-118 (1993); Gaeta and Rink, Med. Chem. Res., 3:483-490 (1994); and, Pittner et al., J. Cell. Biochem., 55S:19-28 (1994). Amylin is the subject of U.S. Pat. No. 5,367,052, issued Nov. 22, 1995.
Excess amylin action has been said to mimic key features of Type 2 diabetes and amylin blockade has been proposed as a novel therapeutic strategy. It has been disclosed in U.S. Pat. No. 5,266,561, issued Nov. 30, 1993, that amylin causes reduction in both basal and insulin-stimulated incorporation of labeled glucose into glycogen in skeletal muscle. The latter effect was also disclosed to be shared by calcitonin gene related peptide (CGRP) (see also Leighton and Cooper, Nature, 335:632-635 (1988)). Amylin and CGRP were approximately equipotent, showing marked activity at 1 to 10 nM. Amylin is also reported to reduce insulin-stimulated uptake of glucose into skeletal muscle and reduce glycogen content (Young et al., Amer. J. Physiol., 259:45746-1 (1990)). The treatment of Type 2 diabetes and insulin resistance with amylin antagonists is disclosed.
In Type 1 diabetes, amylin has been shown to be missing or deficient and combined replacement with insulin has been proposed as a preferred treatment over insulin alone in all forms of diabetes. It has been proposed that the lack of amylin contributes to poor glucose control, especially after eating. Indeed, amylin has been shown to have at least two effects believed to be important for normal glucose metabolism: it slows glucose inflow into the bloodstream from the gastrointestinal tract, and it suppresses glucagon secretion and thereby helps to lower glucose production by the liver.
After a typical meal, over 75 grams of glucose pass from the stomach and gastrointestinal tract, through the bloodstream, and into muscle and liver tissue for storage as glycogen. This amount of glucose is large relative to the five to six grams of glucose typically present at normal concentrations in the blood pool of an average adult. In healthy people, the rate of glucose inflow from the gastrointestinal tract is closely matched with the rate of outflow into the storage tissues, allowing the body to maintain normal blood glucose concentrations. The endocrine regulator of glucose outflow rate is insulin, which is secreted by pancreatic beta-cells in response to rising blood glucose concentrations. The endocrine regulator of glucose inflow rate has, until recently, been unknown.
Now, preclinical and clinical data have confirmed the role of amylin as a key regulator of glucose inflow rate. In animals and humans, rising amylin blood concentrations slow down the transfer of nutrients from the stomach to the intestines. Young et al., Diabetalogia 38:642-648 (1995); Young et al., Metabolism 45:1-3 (1996); Macdonald et al., Diabetalogia 38(supp 1):A32 (1995). This transfer is the rate-limiting step in the appearance of nutrient-derived glucose in the bloodstream. Thus, the simultaneous secretion of both insulin and amylin by the pancreatic beta-cells acts to regulate both inflow and outflow, thereby keeping post-meal blood glucose concentrations within a narrow and healthy range.
Between meals, the liver produces glucose which is carried by the bloodstream to the brain and other tissues that do not store glucose. The endocrine regulator of liver glucose production is glucagon, a peptide hormone secreted by pancreatic alpha-cells in response to falling blood glucose concentrations. At mealtime, glucagon secretion must be suppressed to avoid hyperglycemia induced by excess liver glucose production, and a known regulator of glucagon suppression is insulin. Other preclinical and clinical data support the idea that amylin too is an endocrine regulator of glucagon secretion. In animals and humans, increasing amylin blood concentrations slows pancreatic alpha-cell secretion of glucagon, an effect which amplifies the same regulatory effect of insulin. Gedulin et al., Metabolism 46:67-70 (1997). Thus, the simultaneous secretion of both insulin and amylin by the pancreatic beta-cells can act to suppress glucagon and curtail liver glucose production, thereby helping to keep post-meal blood glucose concentrations within a narrow and healthy range.
The use of amylin and other amylin agonists for the treatment of diabetes mellitus is the subject of U.S. Pat. No. 5,175,145, issued Dec. 29, 1992. Pharmaceutical compositions containing amylin and amylin plus insulin are described in U.S. Pat. No. 5,124,314, issued Jun 23, 1992.
One amylin agonist, pramlintide (.sup.25,28,29 Pro-human amylin, also previously referred to as "AC137"), a synthetic analog of human amylin in which select modifications have been made, is presently undergoing testing in people with Type 1 and Type 2 diabetes who use insulin to control their blood glucose. To confirm that replacing the desired biological actions of amylin, along with insulin, is beneficial compared to the use of insulin alone, Amylin Pharmaceuticals, Inc. (San Diego, Calif.) has conducted extensive preclinical and clinical studies of pramlintide, including eighteen Phase I and II clinical trials involving over 1,000 people with diabetes who use insulin. In seven-out-of-seven Phase II studies assessing glucose control, this amylin agonist analogue caused a statistically significant and clinically relevant reduction in blood glucose. These seven studies evaluated a progression of different endpoint assessments of glucose control including reduction in post-meal glucose concentrations, 24-hour average glucose concentrations, and fructosamine concentrations. Fructosamine is a surrogate marker which reflects average glucose concentrations over the two-to-three weeks prior to testing. Pramlintide has been well tolerated at anticipated therapeutic doses and there have been no clinically important safety concerns. Pramlintide is the subject of U.S. Pat. No. 5,686,411, issued Nov. 11, 1997.
Specifically, in a 14-day, double-blind, placebo-controlled Phase II clinical study completed in 1994, subjects with Type 1 diabetes had a statistically significant reduction in blood-glucose concentrations after a test meal compared to placebo when they self injected pramlintide three times per day in addition to their usual insulin therapy. Results from this study were published in April 1996 in Diabetologia.
In January 1995, results from a placebo-controlled, double-blind, clinical pharmacology study were reported, showing that an intravenous infusion of pramlintide significantly reduced post-meal blood-glucose concentrations in subjects with Type 2 diabetes who use insulin. This finding was similar to previous observations in comparable studies in people with Type 1 diabetes.
Results from this study were presented at the June 1995 annual meeting of the American Diabetes Association and the September 1995 annual meeting of the European Association for the Study of Diabetes.
In February 1995, results from another 14-day, double-blind, placebo-controlled Phase II study in subjects with Type 1 diabetes were reported, which showed that 30-microgram doses of pramlintide self-administered four times per day resulted in a statistically significant reduction in blood-glucose concentrations following a test meal and also significantly reduced the average blood-glucose concentrations over a 24-hour observation period (35 mg/dl, p=0.003) during which patients ingested their usual meals, compared to placebo. Results from this study were presented at the September 1995 annual meeting of the European Association for the Study of Diabetes.
In August 1995, results from a 28-day, double-blind, placebo-controlled Phase II trial in subjects with Type 1 diabetes were reported. This study showed that self-administered, 30-microgram doses of pramlintide four times per day (one before each main meal and a late-night snack) significantly lowered the excessive rise in post-meal blood-glucose concentration, compared to the placebo control group. Using this dosing regimen, the study also confirmed that pramlintide significantly lowered 24-hour average blood-glucose concentrations (31 mg/dl, p=0.009) and fructosamine (33 micromoles/liter, p=0.003), compared to placebo. As in previous studies, the 30-microgram dose of pramlintide was well tolerated. The only adverse effects significantly different from those reported by the placebo group were mild gastrointestinal symptoms in a small number of patients, and those were substantially reduced after the first two weeks of treatment. Results from this study were presented at the June 1996 annual meeting of the American Diabetes Association. At the same meeting, abstracts were presented indicating that it is feasible to mix pramlintide with Humulin.RTM. 70/30 insulin in the same syringe just prior to administration. In this study involving people with Type 1 diabetes, plasma glucose profiles were similar when identical doses of Humulin 70/30 insulin and pramlintide were administered, either as separate injections or mixed in the same syringe immediately prior to injection.
In August 1996, the results of a 28-day, double-blind, placebo-controlled Phase II trial in subjects with Type 2 diabetes who use insulin were also reported. In all dose groups, self-administered pramlintide significantly lowered fructosamine as follows: 30 micrograms four times a day (17.5 micromoles/liter, p=0.029), 60 micrograms four times a day (22.6 micromoles/liter, p=0.001), and 60 micrograms three times a day (24.1 micromoles/liter, p=0.003). These results are similar to the positive findings previously reported in patients with Type 1 diabetes. The reduction in fructosamine in the 60 microgram dose groups represents a 50 to 60% reduction in the excess of fructosamine above the upper limits of the normal range. Therefore, this study demonstrated that three-times-a-day dosing of pramlintide can achieve similar clinical benefits as four-times-a-day dosing in people with Type 2 diabetes who use insulin. The study also corroborated the excellent short-term safety profile that had been observed to date in other clinical trials of pramlintide.
As a result of pioneering work with amylin and the invention of superior agonist analogues of amylin by Amylin Pharmaceuticals, Inc., the use of amylin and agonists of amylin show great therapeutic promise. Now, however, as set forth in the following detailed description of the invention, still further surprising new discoveries and inventions comprising synergistic compositions that include certain insulins and amylin agonist compounds have been made which will help people with diabetes improve their glucose control without imposing unacceptable treatment burdens.